Skip to main content

Full text of "Text Book Of Mechanical Engineering"

See other formats


Reverted Trains.                           523                     *

relatively to A.    We  may vary the experiment   by carrying A                       ^

round L, but so that A does not revolve; then the relative posi-
tions will still be the same, as shewn by a comparison of the                      , i
figures, and L will again make two revolutions while A is carried
once round it.                                                                                                     

Watt's sun and planet gear, Fig. 521, is a practical example
A slight deviation from the rigid vertical occurs at c and d, but
the total result remains; s makes two revs, for one rev. of the
crank.                                                                                                                                       ! j

Case IV.A Reverted Train is where A and L turn on the                         \

same axis.    In Fig. 522, A is fixed and L reverted, while abc                      l'j

shews the train in direct order.

.   .   a x c

1 he tram ratio is - and
b x/

n                  a*c

/ s revs. = i - --

If A  and  L are nearly equal, we may obtain a very slow                           fyj

relative rotation, as in Fowler's first coiling gear, Fig. 523.    Stud                           'i

D supports the drum and gear, A is the fixed wheel, and a dif-                             \

ference of about one tooth in 40 between A and L causes the                           ^1

latter to turn very slowly, rotating the cam  E, and raising or                           Jfji

lowering the coiling lever and guide pullies as required.                                              |l

Fig. 524 has an annular wheel, but is otherwise like Case II.                             
Opening out the train, it is found that while /'s revs, are minus,
those of L are plus, so                          .
L's revs. = i 4- _~

Its application is shewn to a ship's capstan ; and

TT , ~    .       L's revs,     lever arm
Vel. Ratio = - x  -      ,

i          barrel frad.

D being inserted for steadim en t.       s

MoorJs Pulley Block, Fig. 525^15 a ^evirted train with annular
wheels.     Referring to the  lower  diagrams, the  train  ratio   is

~2-~ and a miniis rotation is induced, in / or L by the relative

motion of # or A*                               A x C

.*.. L's revs.  r ~ ~^
.                                   B x'L